Short Barrels/Cartridge Effectiveness

[Nightcrawler]

Short Barreled Rifles are all the rage these days, and in many ways have supplanted the submachine gun as close quarters battle weapons.

You have the M4 Carbine and Colt Commando, and a variety of other midget M16s out there.

You have the Micro Galil.

You have the HK33K and the HK53 (the latter having an 8" barrel).

You have the AKSU-74 and (I think) the AKMSU-47 "Kinkov".

You have the HK G36K and G36C.

Heck, DS Arms even makes an Entry Weapon FAL with an 11.5" barrel. Geez, I'll bet that sucker barks.


At any rate, when you put a pistol cartridge through a 10" or so barrel, it gets an increase in velocity. HOWEVER, when you put a RIFLE cartrige through a barrel less than 20", you're lowering the velocity by every inch you cut. Some cartridges, like 5.56mm, are MEANT to be high velocity.

So, of these four cartridges:

5.56x45mm/.223 Remington
7.62x51mm/.308 Winchester
7.62x39mm ComBloc
5.45x39mm ComBloc

How much velocity/power/effectivness are you losing in a 16" barrel? What about a 10" one? What about ridiculously short barrels, like the 8" on on the HK53?

 

[labgrade]

Essentially these shorties are used in CQB so the velocity issues aren't as definitive as one may think.

Onliest exception I would make is that the bullets should be chosen to reflect that decrease in velocity - i.e. switch to more franibles designed to do similar "duties" at actual velocities.

"High velocity" is relative. Suspect that a 45 gr HP .223 double-tap at "only" 2600 fps will ruin a goblin's day as surely as will a 62 at 2900 fps.

I am baffled at shorties in .308, etc. though. Unless going to a Whisper class, I wonder what's the point ....

 

[CaesarI]

The only one seriously affected in a negative manner is the .223. I remember reading (don't remember where, but it was recent) about velocity tests with the .223. I think you need at least a 15" barrel, maybe as low as 12" in order to keep the bullet above the minimum fragmentation velocity. I remember the CAR was OK, but the G-36C was not (the G-36K is OK though). So it's mostly just the super short barrels that suffer.

If I recall corectly the 5.45X39 never worked as well as our .223 anyway. The 7.62's don't rely on fragmentation (except a particular style of .308 Hirtenberger if I recall), and should expand well enough at most any reasonable velocity.

-Morgan

 

[labgrade]

There's bullets & there's bullets - different jacket thickness/tapers & core hardness. FAIK, LEO-types/entry teamers aren't regulated to military style ammo/bullet construction so could choose more "varmit class" style bullets to give adequate expansion at the (relative) lower velocities.

I think dz posted .223 penetration tests a day or two ago & it has some decent info.

Again, other than supressed Whisper-class .30s, I don't see the point of a .308-class entry weapon other than as a "barrier penetrator" which is served quite well by a 12 gauge. It would seem that .308-class shorties would have extensive muzzle blast, excessive over penetration issues & could be served just as effectively with a 10mm (or so) squirt gun.

 

[Art Eatman]

Nightcrawler, out of my ignorance: Of the guns you've mentioned, how many are actual military-issue, how many are police-issue, and how many are just civilian-oriented para-military?

The reason I ask is that since the 1960s in this country, there has been a "hype" for para-military rifles--semi-auto versions of selective-fire weapons.

(For my generation, "real" rifles are typified by wood stocks and bolt actions. Para-military stuff is fun, but of no particular real-world need.)

To further beat on this horse, the police have become militarized to SWAT teams with special-purpose military-style weaponry. And, the doctrine of armies has changed from long-range shooting to controlling one's environment within 200 yards while calling in air--maximum power or velocity is no longer as important.

, Art